No abstract

The human body and the potential to move it affect the way we perceive the world. Here we explored a possible origin of such action-specific effects on perception. Participants were asked to enclose a virtual object by movements of their index finger and thumb and judged either the actual finger-thumb distance or the size of the virtual object subsequently. The visual-haptic discrepancy that comes with such virtual grasping resulted in a mutual impact of visual and body-related signals: the visual judgments of object's size were attracted by the felt finger posture and vice versa, judged finger distance was attracted by the size of the grasped object. This pattern was observed in spite of a clear spatial separation between somatic and visual signals and was conceptually replicated using a virtual reaching paradigm. The results indicate that basic mechanisms of multisensory integration accompany the emergence of action-specific effects on perception. (PsycINFO Database Record

It has been argued that several reported non-visual influences on perception cannot be truly perceptual. If they were, they should affect the perception of target objects and reference objects used to express perceptual judgments, and thus cancel each other out. This reasoning presumes that non-visual manipulations impact target objects and comparison objects equally. In the present study we show that equalizing a body-related manipulation between target objects and reference objects essentially abolishes the impact of that manipulation so as it should do when that manipulation actually altered perception. Moreover, the manipulation has an impact on judgements when applied to only the target object but not to the reference object, and that impact reverses when only applied to the reference object but not to the target object. A perceptual explanation predicts this reversal, whereas explanations in terms of post-perceptual response biases or demand effects do not. Altogether these results suggest that body-related influences on perception cannot as a whole be attributed to extra-perceptual factors.